4  9.  >>  ft 


Property  of  the  United 


Circular  No    19.  Second  Series      I2o  Ed 


United  States  Department  of  Agriculture, 

DIVISION    OK    ENTOMOLOGY. 


INK  CLOVER  MITE. 
i  Bryobia  prati  >i-i-  <  iai  n 
ill  \K  MJTERISTII  -    Wl>    METHOD   OF    WORK 

The  Bubject  of  this  circular  is  :i  reddish-brown  mite  about  twice  the 
size  of  the  ordinary  red  mite  affecting  greenhouse  plants.  It  is  about 
three-hundredths  of  an  inch  in  length,  oval,  and  with  remarkably  long 
Ulterior  legs.  Other  structural  features,  together  with  tin-  peculiar 
hairs  which  clothe  different  part-  of  the  body,  are  illustrated  in  the 
accompanying  figure,  which  represents,  much  enlarged,  the  full-grown 
mite*,  viewed  from  above  and  from  below. 

This  mite  first  came  into  special  prominence  as  a  disagreeable  invader 
of  dwelling  bouses  aboul  ten  years  since,  hut  it  bad  been  known  for  a 
number  of  year.-  earlier  as  an  enemy  of  various  fruit  and  shade  trees 
and  forage  plants,  its  occurrence  on  clover,  particularly  in  the  Middle 
states,  being  indicated  in  it-  scientific  name,  pratensis,  and  its  com- 
mon name  of  clover  mite.  It  belongs  to  the  family  of  vegetable- 
feeding  mites,  Tetranychide,  which  includes  Buch  well-known  d< 
dators  as  the  red  spider  of  greenhouses,  already  referred  to,  and  the 
potted  mite,  which  is  quite  troublesome  to  oranges  in  Florida. 
In  California,  where  this  plant  mite  is  especially  mischievous,  it  has 
been  very  generally  confounded  with  the  red  spider,  and  in  probably 
most  of  the  references  to  injury  to  deciduous  trees  on  the  Pacific  < 
by  the  "red  Bpider"  the  real  culprit  is  the  insect  under  discussion. 

The  presence  of  this  mite  on  foliage,  either  of  'lover  or  I 
the  leaves  to  yellow,  or  assume  a  Bickly  appearance,  as  if  attacked  by 
a  fungus,  thi  the  tender  leave-  of  clover,  notably  on  the  upper  Bide, 
the  juices  are  extracted,  often  over  irregular,  winding  areas,  imitat- 
ing in  appearance  the  burrows  of  certain  leaf-mining  larva-.  The 
most  notable  indication,  however,  of  the  e  of  the   mite  i-  the 


occurrence  of  the  eggs  massed  often  in  such  numbers  as  to  completely 
cover  the  hark  at  the  crotches  and  branches  and  sometimes  over  the 
entire  surface  of  the  trunk.  These  eggs  are  of  rather  large  size,  of  a 
reddish  color,  and  are  conspicuous  objects.  When  numerous  the 
decided  color  they  impart  to  the  bark  leads  to  their  ready  discovery. 

As  out-of-door  enemies  they  are  injurious  at  times  to  clover  and 
other  grasses,  including  the  true  grasses,  as  blue  stem,  but  it  is  to  fruit 
trees  that  their  injuries  are  especially  marked.  Throughout  the  Pacific 
Coast  and  in  the  fruit  districts  of  Colorado  and  other  Western  mountain 
States  the  clover  mite  is  one  of  the  principal  enemies  of  such  deciduous 
fruits  as  peach,  prune,  plum,  apple,  pear,  almond,  cherry,  etc.,  and  the 
poplar  and  elm,  black  locust,  arborvitse,  etc.,  among  shade  trees.  As 
house  pests  they  are  troublesome  from  their  presence  merely  in  their 
efforts  in  the  fall  to  find  safe  hibernating  quarters  and  occasionally  in 
their  spring  migrations  in  search  of  suitable  breeding  grounds. 

ORIGIN   AND   DISTRIBUTION. 

Attention  was  first  drawn  to  this  mite  in  1879  at  Washington,  D.  C, 
from  its  occurrence  on  the  trees  in  the  Department  grounds  and  also 
on  clover  on  lawns.  It  has  since  been  reported  from  numerous  locali- 
ties from  Massachusetts  to  California.  Northward  it  occurs  in  the  East 
in  northern  New  York  and  Canada.  East  of  the  Mississippi  it  has  not 
been  reported  in  the  southern  tier  of  States,  the  southernmost  records 
occurring  in  Tennessee  and  North  Carolina. 

On  the  Pacific  Coast  it  is  known  from  San  Diego,  Cal.,  to  East 
Sound,  Washington;  and  at  Las  Cruces,  N.  Mex.,  it  is  a  serious  fruit 
pest.  In  the  Sierra  Nevada  Mountains  in  California  and  in  the  Rocky 
Mountains  in  Montana  it  has  been  found  at  elevations  of  from  7,000  to 
8,000  feet. 

It  is  remarkable,  therefore,  for  its  ability  to  exist  under  marked 
differences  of  temperature  and  elevation.  Its  wide  distribution  and 
its  occurrence  in  situations  remote  from  settlement  indicate  that  it  is 
a  native  species.  It  was  first  characterized  scientifically  by  H.  Garman 
in  1885,  who  proposed  for  it  the  common  and  Latin  name  by  which  it 
is  now  known. 

HABITS   AND    LIFE    HISTORY. 

The  wide  range  of  this  insect  and  the  different  climatic  conditions 
under  which  it  exists  lead,  as  might  be  expected,  to  certain  variations 
in  its  life  history  and  habits  in  different  localities.  In  the  more 
northern  regions  of  its  occurrence  and  in  the  higher  elevations  it  win- 
ters in  the  egg  state,  the  last  brood,  if  it  may  be  so  called,  maturing 
in  the  fall,  and  depositing  eggs  on  branches  and  trunks  of  trees  some- 
times in  sufficient  numbers  to  entirely  cover  the  bark  two  or  three 
layers  deep.     In  1889  we  received  a  mass  of  these  eggs  several  layers 


,l"'"' l  Piece  of  bark  which  the  sender  stat  ,„„  an  area  of  il 

'  the  south  side  of  trunks  of  cotton* h 

growing  at  an  elevation  of  from  6,000  to  B.000  feet.     Th  ,  the 


Tu 


olumne  County,  Cal.,  and  we  have  had 


tile    egg   State, 

iv  of  the  young 

following    -yjr 


Sierra  Nevada  Mountain 
a    similar  account,    with 

specimens,  from  Mi  <  Jar- 
tliy  Mountain,  in  Mon- 
tana, at  about  the  same 
elevation.  In  the  Mid- 
dle and  Eastern  States, 
where  the  eggs  are  fre- 
quently found  on  fruit 
trees,  they  arc  usually 
confined  to  the  crotches 
and  branches  and  are 
ti"!  nearly  so  abundant. 
In  the  colder  regions, 

where     the     winter     is 
--■■el  in  the  egg  Btate, 

the  issuance 

mites      th 

Bpring  varies  from   Maj 

until  the  middle  of  June, 

depending  on  the  char- 
acter of  the  Beason.     In 

the  warmer  regions— as, 

for  instance,  in  the  lati- 
tude     of     Washington, 

D.   ('. — the  mites  begin 

to  be  noticeable  on  foli- 
and  grass  in  May  or 

earlier,  and   enter  their 

hibernating     q  uartere 

early  in  October,  in  crev- 

-      Of     truer-     ,  „•     walls. 

<>r  under  the  loose  bark 
of  various  trees.  It  is 
Been,  therefore,  that  in 
the  warmer  localities 
breeding  is  hardly  inter- 
rupted during  the  win- 
^mont^^d  ^  winter  is  passed  quite  as  much  in  the  active  as  in 
the  egg  state.  Ihrou.hout  the  summer  young  are  produced  continu- 
i;m"'  mOSl  0thw  P,an<  ■»**.  with  no  particular  differentiation 


b     ventral 
•'.  I.  a.  mouth  i  , 
•  :  *'.  I.  »i.  !■  Ufe) 


UNIVERSITY  OF  FLORIDA 


3  1262  09216  4994 

The  habit  of  this  mite  of  abandoning  its  feeding  situations  in  the 
fall  to  seek  hibernating  quarters  elsewhere  leads  to  its  being  a  house 
pest  of  no  mean  importance.  This  is  particularly  true  wherever  it 
has  been  breeding  on  clover  or  other  grasses  near  dwellings.  From 
such  situations,  particularly  in  the  Mississippi  Valley  States,  it  often 
swarms  into  dwellings  through  doors  or  windows,  its  small  size  ena- 
bling it  to  penetrate  wire  screens  with  ease,  to  the  very  considerable  dis- 
quietude of  the  housekeeper.  There  are  only  a  few  records  of  their 
entering  houses  in  the  East,  and  in  the  extreme  West  they  seem  only 
to  have  been  found  on  trees. 

REMEDIES    AND    PREVENTIVES. 

The  protection  of  fruit  trees  from  the  attacks  of  this  mite  is  com- 
paratively easy  where  the  winter  is  chiefly  passed  in  the  egg  state,  as 
in  Colorado  and  other  elevated  or  cold  districts.  The  experience  of 
Mr.  C.  P.  Gillette  in  Colorado  has  shown  that  the  eggs  may  be  very 
easily  destroyed  during  the  winter  by  applying  kerosene  emulsion  to 
the  trees  at  about  twice  the  ordinary  strength,  viz,  diluted  with  five 
parts  of  water.  Sprajung  at  this  time  is  both  economical  and  easy, 
on  account  of  the  absence  of  foliage,  and  no  danger  will  result  to  the 
plants  from  the  application.  Such  an  application  also  in  the  warmer 
latitudes 'will  be  of  almost  equal  value  as  a  protection  to  fruit  trees, 
since  it  will  reach  what  eggs  there  may  be  and  also  many  of  the  mites 
secreted  in  the  cracks  of  the  bark. 

It  is  a  much  more  difficult  matter  to  protect  clover  and  other  grasses 
from  the  mites,  except  as  it  may  be  possible  to  spray  in  winter  the 
trees,  fences,  etc.,  on  or  in  which  the  mites  may  be  hibernating,  in  the 
vicinity  of  lawns. 

Their  entrance  into  houses  in  the  fall  may  be  prevented  by  spraying 
the  lower  portion  of  the  building,  walls,  etc.,  with  pure  kerosene  as 
often  as  need  be  and  also  spraying  the  lawns  immediately  about  the 
building  with  kerosene  emulsion  nine  times  diluted.  The  mites  may 
be  destroyed  after  they  have  gained  entrance  to  the  house  by  the  free 
use  of  buhach  or  pyrethrum  powder,  burning  brimstone,  or  spraying 
with  benzine,  taking  due  precautions  with  the  latter  substance  in  the 
matter  of  fire. 

C.  L.  Marlatt. 
First  Assistant  Entomologist. 

Approved : 

James  Wilson, 

Secretary  of  Agriculture. 

Washington,  D.  C,  July  19,  1897. 

O 


